首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10791篇
  免费   472篇
  国内免费   21篇
电工技术   111篇
综合类   4篇
化学工业   2080篇
金属工艺   169篇
机械仪表   210篇
建筑科学   636篇
矿业工程   23篇
能源动力   337篇
轻工业   963篇
水利工程   113篇
石油天然气   30篇
无线电   787篇
一般工业技术   2088篇
冶金工业   1791篇
原子能技术   73篇
自动化技术   1869篇
  2023年   74篇
  2022年   139篇
  2021年   222篇
  2020年   178篇
  2019年   220篇
  2018年   243篇
  2017年   242篇
  2016年   260篇
  2015年   233篇
  2014年   344篇
  2013年   700篇
  2012年   577篇
  2011年   821篇
  2010年   536篇
  2009年   502篇
  2008年   620篇
  2007年   532篇
  2006年   454篇
  2005年   411篇
  2004年   355篇
  2003年   329篇
  2002年   304篇
  2001年   178篇
  2000年   184篇
  1999年   167篇
  1998年   260篇
  1997年   224篇
  1996年   185篇
  1995年   150篇
  1994年   134篇
  1993年   118篇
  1992年   97篇
  1991年   80篇
  1990年   100篇
  1989年   88篇
  1988年   66篇
  1987年   73篇
  1986年   70篇
  1985年   87篇
  1984年   60篇
  1983年   87篇
  1982年   62篇
  1981年   54篇
  1980年   50篇
  1979年   56篇
  1978年   45篇
  1977年   46篇
  1976年   51篇
  1975年   32篇
  1974年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Piaget believed that young children were egocentric and would ascribe their own knowledge to another. In contrast, Wimmer, Hogrefe, and Perner (1988) found that children did not perform egocentrically when assessing another's knowledge. The present study was carried out to determine which claim was right. A familiar object was secretly placed in a box, and a child and others either looked in the box or did not look. Two of the main findings were that (a) 6-year-olds were significantly better than 3- to 4-year-olds at assessing the other's knowledge, even though both assessed the other's perception correctly (p?p?  相似文献   
23.
The group scanning model of feature integration theory suggests that Ss search visual displays serially by groups, but process items within each group in parallel. Group size is determined by the discriminability of the targets in the background of distractors. When the target is poorly discriminable, the size of the scanned group will be small, and search will be slow. The model predicts that group size will be smallest when targets of an intermediate value on a perceptual dimension are presented in a heterogeneous background of distractors that have higher and lower values on the same dimension. Experiment 1 (30 Ss) demonstrates this effect; Exp 2 (12 Ss) controls for a possible confound of decision complexity in Exp 1. For simple feature targets, the group scanning model provides a good account of the visual search process. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
24.
Assessed whether resting anterior asymmetry would discriminate individual differences in repressive-defensive coping styles. In 2 sessions, resting electroencephalogram was recorded from female adults during 8 60-sec baselines. Ss were classified as repressors or nonrepressors on the basis of scores on the Marlowe-Crowne Social Desirability Scale (MC), the State-Trait Anxiety Inventory (STAI), and the Beck Depression Inventory (BDI). In midfrontal and lateral frontal sites, repressors demonstrated relative left hemisphere activation when compared with other groups. The MC, but not the STAI or the BDI, contributed unique variance to frontal asymmetry. Relative left frontal activation may be linked to a self-enhancing regulatory style that promotes lowered risk for psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
25.
A new method of cryptologic attack on binary sequences is given, using their linear complexities relative to odd prime numbers. We show that, relative to a particular prime number p, the linear complexity of a binary geometric sequence is low. It is also shown that the prime p can be determined with high probability by a randomized algorithm if a number of bits much smaller than the linear complexity is known. This determination is made by exploiting the imbalance in the number of zeros and ones in the sequences in question, and uses a new statistical measure, the partial imbalance.This project was sponsored by the National Security Agency under Grant No. MDA904-91-H-0012. The United States Government is authorized to reproduce and distribute reprints notwithstanding any copyright notation hereon.  相似文献   
26.
A numerical model for non-linear static and dynamic analysis of stiffened box structures is presented. The model is based on a new super element formulation which provides complete C1 continuity for both plate and beam elements. Geometric and material non-linearities are included and the temporal equations are solved by the implicit Newmark-β method with Newton-Raphson subiteration. The new formulation has been applied to the static, vibration and transient analysis of various structures such as flat plates, folded plates and rectangular boxes. Both isotropic and beam stiffened structures are considered and the results obtained are compared with other available solutions. It is observed that the new super element formulation can provide reasonable solutions to both linear and non-linear problems of stiffened box structures. The mathematical formulation of the model is presented in this paper, while the numerical verifications are given in the companion paper.1  相似文献   
27.
Evaluated the validity of self-efficacy expectations as predictors of mortality for 119 patients with chronic obstructive pulmonary disease. Ss completed 4 physiological measures that represent common clinical indicators of disease severity: forced expiratory volume in 1 s(FEV1.0), arterial blood gas measurement of resting partial pressure of oxygen (PaO?), single-breath diffusing capacity (DLCO), and maximum oxygen uptake (V02max) during exercise. In addition, self-reported self-efficacy expectation for walking on a treadmill was measured. Self-efficacy was a significant univariate predictor of 5-yr survival. However, when controlling for FEV1.0 in multivariate survival analysis, self-efficacy had only a marginal effect. Simple self-report scales may provide significant information about health status. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
28.
Examined pre- and posttreatment changes in life stressors and social resources and their association with treatment outcomes in a 12-mo follow-up of 424 Ss (aged 18–83 yrs) with unipolar depression. Assessment measures included the Family Environment Scale, Work Environment Scale, and Health and Daily Living Form. As expected, Ss reported significant, multidimensional improvements in their functioning at follow-up. There were modest increases in Ss' social resources but, suprisingly, no overall decrease in stressors. Life stress and resource factors were significantly related to Ss' functioning at follow-up, even after considering the severity of their dysfunction at treatment intake and their length of treatment. Implications for developing a general body of knowledge about the process of recovery and relapse in behavioral disorders are discussed. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
29.
A method is presented for the fully automatic conversion of a general finite element mesh containing triangular elements into a mesh composed of exclusively quadrilateral elements. The initial mesh may be constructed of entirely triangular elements or may consist of a mixture of triangular and quadrilateral elements. The technique used employs heuristic procedures and criteria to selectively combine adjacent triangular elements into quadrilaterals based on preestablished criteria for element quality. Additional procedures are included to eliminate isolated triangles. The methods operates completely without user intervention once the nodal co-ordinates and element connectivity of the original mesh are supplied.  相似文献   
30.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号